The present invention relates to a lubricating method and a lubrication device for an internal combustion engine, and in particular, though not limited thereto, to a method and a device suitable for lubricating an engine used as a power source for compact working machines such as a portable trimmer, a lawn mower, a chain saw or the like.
A portable type working machine represented by a trimmer and a chain saw is required to allow an operator to work without any restriction on his working posture. Accordingly, an internal combustion engine mounted on such working machines as a power source is required to constantly provide a stable operation even if the machine is used in a working posture of, for example, laterally tilted position.
In order to meet this requirement, a compact air-cooled type two stroke cycle gasoline engine (hereafter, the xe2x80x9ctwo stroke cycle enginexe2x80x9d) has been conventionally used. Such a two stroke cycle engine uses a mixed fuel composed of a fuel and a lubricant oil which is mixed in a certain ratio. However, the two stroke cycle engine has some disadvantages in that it is difficult to take an effective purifying measure against the exhaust gas or an emission gas. This is because the two stroke cycle engine generates an exhaust gas containing a large amount of unburned gas constituent due to a gas-flow type scavenging system employed therein.
As for the purifying measures against the emission gas, a four stroke cycle internal combustion engine (Otto engine, hereinafter, the xe2x80x9cfour stroke cycle enginexe2x80x9d) has an advantage over the two stroke cycle engine because it generates a small amount of unburned gas. Therefore, the four stroke cycle engine is considered to be employed also in the portable working machines in place of the two stroke cycle engine. The four stroke cycle engine typically has an oil reservoir formed by an oil pan disposed in a bottom portion of a crank chamber, so that a lubricating oil contained in the oil reservoir is pumped up by a pump and/or is splashed up by a rotary member, typically, an oil dipper.
A lubricating system using an oil pump, however, is not suitable for portable working machines since an additional mechanism for discharging and recovering the lubricating oil has to be employed. Therefore, the system tends to be complicated and heavy. In addition, a lubricating system using an oil dipper has a shortcoming in that it is troublesome to determine a length of the oil dipper in an engine design process. That is, if the length of the oil dipper is too short, a desired amount of oil lubrication may not be supplied by the oil dipper after a short period of time when the oil is consumed. On the contrary, if the length of the oil dipper is too long, a large amount of oil may be splashed up by the oil dipper right after the oil has been filled into the oil pan and oil mist generated in the crank chamber shall be too rich, i.e., an excessive amount of oil shall be supplied. Such an event might cause a problem of contamination by a blow-by gas.
The present invention is made in the process of a technology developing activity for improving the lubricating system by the oil dipper in response to a current environmental and social request surrounding the engine for portable working machines.
Accordingly, an object of the present invention is to provide an improved lubricating method and device for an internal combustion engine which are an improvement from those in the prior art.
Another object of the present invention is to provide an improved lubricating method and device for an internal combustion engine which allow the engine to be lubricated by taking advantage of engine vibration without using an additional power source.
Yet another object of the present invention is to provide a lubricating device for an internal combustion engine which allows an amount of oil mist to be easily controlled.
The object of the present invention described is accomplished by a method for lubricating an internal combustion engine which includes ruffling an engine oil stored in an oil reservoir located adjacent to a crank chamber to introduce the engine oil into the crank chamber; and impinging a crankshaft provided in the crank chamber on the engine oil to form oil mist.
Further, the object of the present invention described is also accomplished by a lubrication device for an internal combustion engine and includes: a crank chamber; a crankshaft accommodated within the crank chamber; an oil reservoir arranged adjacent to the crank chamber; an engine oil accommodated within the oil reservoir; and a spring member arranged within the oil reservoir so as to be oscillated by an engine vibration.
Further, in an preferred embodiment of the present invention, an engine vibration device is employed to oscillate a spring member to agitate the engine oil in the oil reservoir to splash it up and/or to ruffle its oil surface so as to introduce the engine oil into the crank chamber. A rotating crank shaft impinges on the engine oil within the crank chamber to be formed into fine oil droplets.
A coil spring or a leaf spring may be employed as the spring member. This spring member may be selected based on its natural frequency so as to resonate with, for example, an engine vibration during idle running.
The crank chamber and the oil reservoir may be separated from each other by a partition wall having an opening formed therein and equipped with a net member covering the opening. The net member may control an amount of engine oil to be introduced into the crank chamber allowing an appropriate amount of oil mist to be held in the crank chamber.
Other objects and an action and effect of the present invention will be made obvious by the description of the preferred embodiments of the present invention shown below.